NPPL(A) -> LAPL(A) was simple paperwork and cheque. LAPL(A) -> PPL(A) requires only 15 hours of training & supervised solo.
As a glider pilot I benefitted from the max allowed 10 hour reduction in the PPL syllabus so still had to do 35 hours of training before the flight test. I can't remember what allowances were given to NPPL(A) holders seeking an ICAO PPL but but I'm pretty sure they had to do more than 15 hours additional training & supervised solo. EASA regulations were pretty mush copy/pasted into UK law at Brexit. Recreating a NPPL(A) -> PPL(A) route would require changing the law, removing the 2018 cut-off for NPPL(A) -> LAPL(A) can apparently be done as a purely bureaucratic stroke of a pen.